Generally there is a limit to keeping a room under comfortable thermal conditions for the human body by an air-conditioning system which controls only room-temperature; therefore it is necessary to estimate the actual residential thermal environment by other factors of the thermal environment, that is, the total physical quantities of the speed of the air flow, the humidity, and the radiation. And to detect said thermal conditions, it is required that a thermal-environment sensor should be composed so as to have a mutual thermal relationship between said sensor and the human body based on the thermal equilibrium of the human body.
It should be noted, as disclosed in the official gazette, TOKKAISHO No. 58-218624 in Japan, that a similar kind of sensor exists, which comprises an electric heating element having an electric heater in an empty shell and a thermometer for measuring the surface temperature of said heating element, and which detects thermal conditions in an indoor environment considering the radiation by measuring the surface temperature of said heating element after supplying it with the predetermined thermal quantity by feeding an electric flow to said electric heater.
In the above conventional type sensor, the emissivity of the outer surface of the heating element closely conforms to the emissivity of the surface of the human skin or clothes thereon so as to establish a correlation regarding the thermal equilibrium between the sensor and the human body, considering radiation. But this sensor can detect only the rate of radiation and emission of a heat radiator (the heating element and the human body) with emissivity, whereas the rate of absorption of incident radiation from the outside (radiation from the wall and solar radiation) cannot be detected precisely. That is, regarding radiation from an object which has a similar temperature to the heat radiation (the heating element and the human body) such as radiation from the wall, emissivity is closely equal to absorptivity because the spectral distribution of the radiation is similar to that of the incidence, but regarding extraneous incident radiation in which there is a difference between the spectral distribution of radiation and that of the incidence, such as solar radiation or radiation from a heating apparatus, emissivity and absorptivity in said radiator (the heating element and the human body) do not always conform to each other. Therefore, if the spectral emissivity (equal to the spectral absorptivity) of said heating element does not conform to the spectral emissivity (equal to the spectral absorptivity) of the human body, in the case that there is a difference between the spectral distribution of radiation and that of the incidence, it is difficult to accurately detect the thermal environment due to the low accuracy of substantial conformity in the correlation regarding thermal characteristics between the surface of the sensor and that of the human body.
In regard to this point, the correlation regarding thermal characteristics between the above-composed thermal-environment sensor and the human body is described in detail as follows:
that is, the thermal equilibrium expression of said thermal-environment sensor is given by: EQU M=hgr(Tg-Tr)+hgc(Tg-Ta) [1] PA1 (whereas, M: the supplied thermal quantity; Tg: the surface temperature of the heating element; Tr: the mean radiant temperature in a room environment; Ta: the temperature of the air; hgr: the radiant heat transfer coefficient of the heating element; hgc: the convective heat transfer coefficient of the heating elememt). PA1 (whereas, hr: the radiant heat transfer coefficient of the human body; hc: the convective heat transfer coefficient of the human body; .phi.a: the relative humidity; Psk: the saturated vapor pressure under the mean temperature of the human skin, Tsk; Pa: the saturated vapor pressure under the temperature of the air, Ta; w: the rate of the wet area of the skin; Fcl: a coefficient of the heat resistance of clothes; Fpcl: the transmission coefficient of the clothes against vapor evaporated from the surface of the human skin to the surroundings thereof; k: 2.2 at sea level, the Lewis relationship). PA1 (whereas, hcs: the convective heat transfer coefficient of the human body in the standard air flow; hs: the heat transfer coefficient, the sum of the radiant heat transfer coefficient, hr of the human body and the convective heat transfer coefficient hcs of the human body in a normal state; Pset*: the saturated vapor pressure under SET:; Fcls: the coefficient of heat resistance in the case of the quantity of the clothes equal to 0.6 clo; Fpcls: the transmission coefficient of the clothes against evaporated water vapor in the case of the quantity of clothes equal to 0.6 clo). PA1 (whereas, hc': the convective heat transfer coefficient of the human body considering evaporation), PA1 (hereinafter, the surface temperature of said heating element with characteristics meeting said expressions [9] to [11] is expressed as KET*). PA1 (whereas, hs': the total heat transfer coefficient of the human body by convection, evaporation, and radiation in a standard air flow). PA1 (whereas, M: the generated heat value per a unit surface area of the human body; H.sub.1 : the heat value of an electric heater of the conventional type of the thermal-environment sensor in which the whole shell is heated; A.sub.1 : the effective surface area of the conventional type of thermal-environment sensor in which the whole shell is heated; A.sub.2 : the heat value of the electric heater of the thermal-environment sensor in this invention; A.sub.2 : the effective surface area of the thermal-environment sensor of this invention, that is, the surface area of the electric heater). PA1 (whereas, Nu: Nusselt's number, Re: Reynold's number) PA1 (whereas, Tr: the mean radiant temperature in the room; Ta: the temperature of the air; hgr: the radiant heat transfer coefficient of the heating element; hgc: convective heat transfer coefficient of the heating element). PA1 (whereas, D: the diameter of a spherical shell; .lambda.: the thermal conductivity of the air; U: the speed of the air flow; .nu.: the dynamic coefficient of the viscosity of the air),
Meanwhile, the expression which calculates heat, Hsk lost from the human skin under the optional variable temperature environments is: EQU Hsk=R+C+E [2],
in this case, R, C, and E express each thermal loss by radiation, convection, and evaporation from the human body, and the expression of each thermal loss of the above-mentioned R, C, and E is as follows: EQU R=hr.multidot.Fcl.multidot.(Tsk-Tr) [3] EQU C=hc.multidot.Fcl.multidot.(Tsk-Ta) [4] EQU E=w.multidot.k.multidot.h.sub.3 .multidot.Fpcl.multidot.(Psk-.phi.a.multidot.Pa) [5]
In the case of estimating thermal comfort in a room by adopting the new standard effective temperature, SET* -which has a close relationship to the sense of coldness or warmth and the comfortableness of the human body, and which was set by ASHRAE, the American Society of Heating-Refrigerating and Air-conditioning Engineers in the U.S.A.-, is determined as follows so that the thermal loss calculated based on that theory is equal to Hsk in the above expression [2]: EQU Hsk=hs.multidot.Fcls.multidot.(Tsk-SET*)+w.multidot.k.multidot.hcs.multidot .Fpcls.multidot.(Psk-0.5Pset*) [6]
In other words, SET* is the temperature defined as the uniform temperature environment under which the heat value equal to Hsk given by the expression [2] can be lost in a normal state (the quantity of clothes equal to 0.6 clo; the speed of the air flow equal to 0.1 m/s to 0.15 m/s; the humidity equal to 50%, Tr=Ta) and in the equal physiology state (equal conditions regarding Tsk, w), and moreover, SET* depends on the thermal conditions in the room, namely, the temperature of the air, Ta; the mean radiant temperature, Tr; the speed of the air flow: for example, when the speed of the air flow is 0.1 m/s to 0.15 m/s in a normal state where the quantity of clothes is 0.6 clo; the humidity is 50%; generated heat quantity is 1 Met (=58.2 W/m.sup.2), if SET* is 22.2.degree. C. to 25.6.degree. C., ASHRAE agreed that more than 80% of people feel comfortable in the thermal environment.
In the above thermal equilibrium expression [2] for the human body, by establishing the situation without an action for perspiration of the human body (w=0.06) to consider evaporative heat loss and a range of comfortable temperatures (the temperature of the air is 22.degree. C. to 26.degree. C.) and also by establishing the condition that the relative humidity .phi.a is set at 0.5, the right side, C+E is approximately concluded as follows: EQU C+E=hc'.multidot.Fcl.multidot.(Tsk-Ta) [7]
then, said expression [2] is replaced by: EQU Hsk/Fcl=hr(Tsk-Tr)+hc'(Tsk-Ta) [8]
And comparing said expression [1] with said expression [8] establishes the following relationship: EQU hgr=hr [9] EQU hgc=hc' [10] EQU M=Hsk/Fcl [11]
then, the surface temperature of said heating element, Tg is equal to the mean temperature of the human skin, Tsk, which results in: EQU Tg=Tsk [12]
Furthermore, regading said SET*, evaporative heat loss is included in heat loss by convection, and then said expression [6] results in: EQU Hsk=hs'.multidot.Fcls(Tsk-SET*) [13]
And said expressions [12] and [13] results in: EQU SET*=KET*-Hsk/(Fcls.multidot.hs') [14],
and when calculating in the range of comfortable temperatures, the 2nd term of the right side in said expression [14] can be regarded to be constant.
Accordingly, by measuring the surface temperature, KET* of said heating element with the characteristics of heat transfer which meet the conditions of the expressions [9] [11], SET* can be calculated approximately and the thermal estimation can be executed strictly under the actual residential environment by said thermal-environment sensor.
Therefore, the 1st purpose of this invention is to detect the actual thermal environment in a room with high accuracy, closely approximating the detecting characteristics of a thermal-environment sensor to actual bodily sensations by specifying the characteristics of radiation and absorption of the surface of a heating element with spectral emissivity--which is the function of wavelength-so as to correspond to the extraneous incidence spectrum, so that said expression [9] can be satisfied. In other words, so the radiant heat transfer coefficient of the surface of said thermal-environment sensor, hgr can conform to that of the human body, hr.
And in said conventional sensor equipped with a heating element having an electric heater in an empty shell, decreasing the supplied electric quantity by shortening the diameter of the shell (the heating element) increases the error between the actual effective temperature and the output value of said thermal-environment sensor, which defeats the essential function of the thermal-environment sensor to establish a thermal correlation with the human body. The concrete explanation of this is as follows:
the error between SET* (the index adopted by the American Society of Heating-Refrigerating and Air-conditioning Engineers, ASHRAE in the U.S.A.; the new standard effective temperature which has a close relationship with the sense of warmth or coldness, and comfort of the human body) and KET* (the output temperature of said thermal-environment sensor) is increased by shortening the diameter of said heating element as illustrated in FIGS. 2 and 3. That is, FIG. 2 illustrates the mean square value of the difference between SET* and KET* as S regarding the diameter of the spherical shell, D in the case that the speed of the air flow varies between 0.1 m/s and 1.0 m/s. FIG. 3 illustrates the mean square value of the difference between SET* and KET* as S regarding the diameter of spherical shell, D in the case that the difference between the mean radiation temperature and the temperature of the air varies between 0.degree. C. and 10.degree. C. Therefore, by FIGS. 2 and 3, it becomes clear that the error, S increases as the diameter, D becomes smaller than 100 mm, and that the lowest limit is about 60 mm as the range of the allowable error.
From this viewpoint, it is desirable to detect the thermal conditions at the place where the person is, by putting said thermal-environment sensor near the human body in order to keep a room in a comfortable thermal condition for the human body. But nevertheless, in the above-mentioned case, this requirement cannot be satisfied, because the diameter of the shell cannot be shortened under the predetermined value, and moreover, the large quantity of the supplied electric power requires a supplied electric cord from a commercial electric source, which cannot allow said thermal-environment sensor to be carried freely, so the field of movement is limited. In addition, there exists the practical inconvenience of tripping over said supplied electric cord.
For this reason, the 2nd purpose of this invention is to be able to detect the thermal environment near the human body precisely by the following method:
the composition of said thermal-environment sensor is reformed as follows: that is, the electric heater is installed in part of the heat insulator; and in this way, the newly devised sensor becomes a partial heated sensor, while the conventional one is a whole heated one; by means of this partial heated sensor, the effective temperature considering the temperature of the air, the speed of the air flow, and the radiation can be detected: therefore, this makes it possible to decrease the quantity of electricity and to supply said heater with electric power from an electric battery without an electric cord from a commercial electric source.
In addition, the conventional type considers only the dry heat loss from the human body by radiation and convection, and does not include evaporative heat loss which is caused by perspiration, etc. Therefore, it is difficult to detect thermal conditions in an actual residential environment as precisely as bodily sensations.
For this reason, the 3rd purpose of this invention is to detect more precisely actual thermal conditions in a room by considering heat loss due to perspiration of the human body and by keeping the size of said heating element and the supplied thermal quantity within the most reasonable range to satisfy the condition of evaporative heat loss so as to approximate said thermal-environment sensor to the actual sensations of the human body more precisely.
And the expression of thermal equilibrium regarding said thermal-environment sensor is said expression [1] as above-mentioned, and by this expression, thermal conditions in an indoor environment are determined; in this theory, the condition of equability of the heat flux becomes the premise thereof. While, in the case of said conventional type, there is a problem that the precision thereof is low because the condition of equability of the heat flux is not sufficiently satisfied, since the electric heater is simply placed near the center of the inside of the empty shell and only the upper part of the shell is heated mainly by convective heat transfer as above-mentioned.
The 4th purpose of this invention is to seek improvement in the precision of thermal detecting, by satisfying the conditions of the equability of heat flux that is the premise of the theory of said thermal-environment sensor as much as possible by heating the whole shell equally during the heat transfer from said electric heater to said shell.
And the 5th purpose of this invention is to control the thermal environment precisely by reckoning with all the factors of the thermal environment by detecting the effective temperature considering the humidity as well as the temperature of the air, the speed of the air flow, and the radiation, since the actual thermal environment cannot be otherwise grasped precisely, and the effective temperature depends on the variation of the humidity, even though the temperature, the speed of the air flow and the radiation in a room are under the same conditions.
Moveover, the effective temperature depends on the variation of the quantity of clothes of the users, such as the variation of clothes due to the seasons (for example, summer clothes and winter clothes) and due to whethter or not bedclothes are used on the bed, even though the thermal environment is the same in terms of the temperature of the air, the speed of the air flow, and the radiation, etc.
In other words, the 6th purpose of this invention is to grasp precisely control the actual effective temperature adjusted to the quantity of clothes of the users by detecting the effective temperature reckoning with the quantity of the clothes of the users in addition to the temperature of the air, the speed of the air flow, and the radiation including the humidity in the environment of a room.
In addition, it is known that a sense of draft is caused in heating a room when the speed of the air flow in the room is in excess of a certain value; therefore, it is necessary that the properties of the air flow blowing from the air-conditioning system are controlled. It should be noted that the conventional type does not have the capacity to detect each physical quantity individually, such as the speed of the air flow and the mean radiation temperature, etc., because said conventional type detects the effective temperature simply reckoning with heat loss by radiation, convection, and evaporation of water from the human body; therefore, it is difficult to control the air-conditioning system in the optimum way by detecting directly the speed of the air flow and a sense of draft near the human body.
For this reason, the 7th purpose of this invention is to detect the speed of the air flow and the mean radiation temperature which are important in controlling the thermal environment in a room, while detecting the effective temperature reckoning with heat loss by radiation, convection, and evaporative heat loss from the human body.